Radiation hardness study of CMOS image sensor for 3D Scanning
OMA fellow Samuele Cotta recently spent a week at LMU University in Munich to perform tests with radioactive sources. Samuele is undertaking research at ViALUX GmbH, a German company, and he is also enrolled in a PhD program at LMU under the supervision of Prof. Katia Parodi, so this was also an opportunity for him to get in touch with the research groups and the other PhD students at LMU. In particular the tests were performed under the supervision and with the help of Dr. Peter Thirolf and his group.
Samuele is currently studying the radiation hardness of a CMOS image sensor that will be used in a 3D scanning device for radiotherapy. Scattered photons and photoneutrons can cause errors and/or damage in the devices used in the conventional radiotherapy treatment rooms. In particular, the dose absorbed in the CMOS sensor can contribute to its performance degradation. In order to collect data about the effects caused by the secondary photons, the CMOS sensor was exposed to different gamma sources, each one with specific photon energies, covering the energy range of the secondary photons in the treatment rooms ( 100keV - 1MeV). The differences in the CMOS performance before and after the irradiation are now under study.
The ViALUX electronics and the 3D scanner device that are currently under test (image courtesy of ViALUX GmbH).
During irradiation the CMOS sensor was shielded from the visible light, in order to acquire only the signals due to the radioactive sources. These data will be then combined with Monte Carlo simulations to study if the dose absorbed by the CMOS sensor can be estimated from the data acquired by the sensor itself.
The next step in Samuele’s project will be to test the effects of the thermal and fast neutrons on different electronic components and on a complete 3D scanning device. These tests will be performed at the nuclear reactor FRM II in Garching bei München, thanks to the collaboration with TUM University in Munich.